The approaches described in this section could be pursued, but are not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
In computer networks such as the Internet, packets of data are sent from a source to a destination via a network of elements including links (communication paths such as telephone lines, wires or cables, or optical lines) and nodes (for example, switches or routers directing the packet along one or more of a plurality of links connected to the switches or routers) according to one of various routing protocols.
One class of routing protocol comprises Routing Vector Protocols according to which the path to a network destination is determined based on a reachability metric. One such protocol comprises a distance vector protocol such as the Routing Information Protocol (RIP) which is described in Internet Engineering Task Force (IETF) Request for Comments (RFC) 1058 and 1723.
A problem that arises with routing vector protocols such as RIP is that if a component fails in the network then packets may be lost while the network converges on a changed topology. For example if node A fails then according to normal forwarding, until node B has updated its forwarding information base, it will forward packets for nodes A and D to node A and those packets will be lost.
One solution that has been proposed to this problem is described in co-pending patent application Ser. No. 11/526,933 filed 25 Sep. 2006, entitled “Forwarding data in a data communications network” of Stewart Bryant et al (“Bryant et al”) the entire contents of which are incorporated by reference for all purposes as if fully set forth herein. According to this approach repair paths are computed. However computation of repair paths can be burdensome as large numbers of candidate routes may be available.